The seronin or 5-hydroxytryptamine (5-HT) is a biogenic amine involved in diverse physiologic and physiopathological processes in the cardiovascular system. 5-HT may lower the arterial blood pressure by an action on central 5-HT1A receptors, or may increase it by stimulation of 5-HT2 receptors located in vascular smooth muscle. It has been postulated that hypofunction of 5-HT1A receptors, or the exaggerated stimulation of 5-HT2 receptor may be associated with arterial hypertension and that agonists of the first type (indorenate or 8-OH-DPAT) or antagonists of the second type (ketanserin or pelanserin) allow the control of arterial hypertension. On the other land, ketanserin and pelanserin attenuated the hemodynamic manifestations in an experimental model of thromboembolism, suggesting that 5-HT is involved in such phenomenon. Finally, 5-HT could be related with the presence of angor pectoris during hypertension or atherosclerosis, diseases that are associated with a lesional of the vascular endothelium, a condition that favors the 5-HT induced vasoconstriction in coronary arteries.

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[Dipeptidase activity and protein absorption in rats maintained on an alcoholic diet for 6 months].

Rats treated with ethanol during 10 to 14 weeks, do not present alteration of protein absorption in spite of alcohol's inhibiting action on amino acid transport. In these animals, intestinal dypeptidase activity at 24 weeks was similar in the alcoholic rats and in the control group, which may possibly be the explanation for the normal protein absorption.

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PubMedDate not supplied

[An analysis of the antihypertensive properties of 3-nitropropionic acid, a compound from plants in the genus Astragalus].

3-Nitropropionic acid (NPA), a compound obtained from Astragalus species, elicited a dose-dependent relaxation of precontracted rabbit aortic rings. The remotion of endothelium or the presence of atropine, propranolol or brompheniramine did not modify the vasodilator effect of NPA but methylene blue clearly inhibited it. On the other hand the acute i.v. administration of NPA in normotensive rats or the chronic oral administration of NPA in renal hypertensive dogs, provoked both a decrease in blood pressure and bradycardia. Finally, NPA elicited negative inotropic and chronotropic effects in guinea pig isolated auricles, which were not blocked by atropine and it inhibited the increase in contractile force and heart rate elicited by isoproterenol. The present results indicate that NPA has vasodilator and antihypertensive properties. The arterial relaxation elicited by NPA was inhibited with methylene blue suggesting that it is a consequence of guanylate cyclase stimulation. The hypotensive effect was independent of the animal species or route of administration used. The bradycardia seen in rats and dogs and the negative chronotropic and inotropic effects observed in isolated auricles suggest that the hypotensive effect of NPA is a mixture of vasodilator and cardiodepressor actions. NPA cardiac effects may be related with inhibition of beta-adrenergic mediated responses.

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PubMedDate not supplied

[Differences between the effects of indorenate and other 5-HT1A agonists on the rabbit aorta].

The aim of this study was to determine if like buspirone, ipsapirone and 8-hydroxy-2(di-N-propylamino)tetralin (8-OH-DPAT), the alpha 1-adrenoceptors are involved in the responses elicited by indorenate in rabbit aorta. Exception made of ipsapirone, all the 5-HT1A agonists above mentioned contracted aortic rings. The contraction elicited by buspirone and 8-OH-DPAT was blocked with prazosin (alpha 1-adrenergic antagonist), whereas the effect of indorenate was unaffected with this blocker but it was inhibited with ritanserin (5-HT2 antagonist). On the other hand, buspirone, ipsapirone and 8-OH-DPAT but not indorenate relaxed arteries precontracted with methoxamine (alpha 1-adrenergic agonist) and none of the agonists relaxed preparations precontracted with acetylcholine or KCl. The results indicate that buspirone and 8-OH-DPAT are partial alpha 1-adrenoceptor agonists since they elicited contractions which are blocked with prazosin and relaxed only rings precontracted with methoxamine. Ipsapirone behaved as an alpha 1-adrenoceptor antagonist since it showed the relaxant but not the contractile effect. Finally, we found no evidence that indorenate has afinity for alpha 1-adrenoceptors. Contraction elicited by this agonist seems to be mediated by 5-HT2 receptors, inasmuch it was blocked with ritanserin.

5-Methoxytryptamine↗

PubMedDate not supplied

Droperidol interacts with vascular serotonin receptors and alpha-adrenoceptors.

This investigation was performed to determine whether droperidol interacts with 5-hydroxytryptamine (serotonin) receptors in the rat aorta. Droperidol caused concentration-dependent vasorelaxation in endothelium-intact and endothelium-denuded aortic rings precontracted with noradrenaline or 5-hydroxytryptamine. Conversely, the contractile effect of prostaglandin F2 alpha was not affected by droperidol. Pretreatment with propranolol, brompheniramine and atropine (10(-6) M each) did not alter the relaxant effects of droperidol. In addition, droperidol shifted the 5-hydroxytryptamine and noradrenaline concentration-response curves to the right in an apparently competitive manner. However, prazosin did not modify the concentration-response curve to 5-hydroxytryptamine, which is consistent with the hypothesis that the latter has an intrinsic efficacy for non-alpha 1-adrenoceptors. These results strongly suggest that a direct arterial endothelium-independent relaxant action of droperidol can be attributed to a 5-hydroxytryptamine receptor-blocking property and support its vascular alpha-adrenoceptor-blocking effect.

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